1. Field of the Invention
The present invention relates generally to semiconductor device fabrication, and more particularly to semiconductor wafer processing systems.
2. Description of the Background Art
A typical semiconductor wafer processing system has a process module (also known as a “reactor” or “process chamber”) for processing semiconductor wafers and wafer handling modules for moving the wafers in and out of the process chamber. Process modules are available for chemical vapor deposition, physical vapor deposition, etching, electro-plating/electro-fill, and other semiconductor device fabrication processes. For example, a chemical vapor deposition module may be used to deposit a film of dielectric material on a wafer.
Wafer handling modules employ manipulators, such as robots, for transporting wafers between two locations of a wafer processing system. A wafer placed in a loading station is picked-up by a robot and goes through a series of intermediate chambers before reaching the process module where the wafer is processed. In a so-called cluster tool, these intermediate chambers may include aligners, indexers, load locks, transfer chambers, heating stations, and cooling stations. For example, a wafer is ordinarily transferred from a load lock to a process module via an intermediate transfer chamber, which houses a vacuum robot for handling the wafer.
Throughput is a measure of the processing speed of a wafer processing system. The higher the throughput, the more wafers that can be processed within a given amount of time. Thus, it is desirable to have a wafer processing system with high throughput.
It is also desirable to minimize the component count of the wafer processing system. Low component count not only decreases the cost of the wafer processing system, but makes it more reliable as well.